One of the things that puzzles me is the people who complain about giving up their privacy when they join Web sites designed to take their privacy away from them.

For example, all email is an open book. You can see that clearly, by reading or listening to stories about former Gen. and CIA Director David Petraeus and all the trouble he is having with women.

The trouble came after the FBI read emails his girlfriend and biographer, Paula Broadwell, sent to another woman he knew named Jill Kelley.

Anyone would think that the director of the CIA would know how to keep emails a secret, especially emails that would turn him into an international laughingstock. But no.

The email gremlins have all emailers in a toehold every time the mailers hit send. They will twist the toes they hold in a heartbeat.

It is true most email is vacuous junk in which nobody is interested. The same is true of tweets, whatever those are, and of stuff people put on Facebook. But whether you like it or not, all your most intimate thoughts, along with your driver’s license number and your shoe size are out there for anybody to find out about, and in many cases use to track you around and sell you things.

The same is not true of the U.S. Mail. Unless someone breaks the law and opens a piece of mail you have sent, it will arrive without anyone seeing it except the recipient. Unless the recipient passes it around, what is written is private.

Nobody is saying normal mail should be open to all eyes. In fact, that would be insane to propose. It would be laughed out of Congress. But email can be subject to all eyes, from those of the FBI to those of reporters.